Polymer network with triple shape effect and associated programming method

ABSTRACT

The invention relates to a polymer network with triple-shape-memory effect and an associated programming method. The invention also relates to a method for producing layer systems made of shape-memory materials comprising the polymer network. The polymer network includes
         A) a first crystalline switching segment made of a star polymer; and   B) a second crystalline switching segment made of a linear polymer or a star polymer.

The invention relates to a polymer network with triple-shape-memoryeffect and an associated programming method. The invention also relatesto a method for producing layer systems made from polymer shape-memorymaterials.

STATE-OF-THE-ART AND BACKGROUND OF THE INVENTION

Unlike dual-shape-memory polymers which have been summarized in theliterature and which can accomplish the network formation by bothphysical interactions as well as by covalent bonds, triple-shape-memorypolymers have thus far been described only as networks based on covalentbonds [Bellin, I. et al., Polymer triple-shape materials, PNAS (2006),103(48), p. 18043-18047]. Such triple-shape-memory polymer networksconsist of at least one type of covalent cross-linking sites and atleast two types of switching segments. In analogy to a dual-shape-memorypolymer networks, triple-shape-memory polymer networks may contain,among others, segments of poly(ε-caprolactone), polyethers, polyetherurethanes, polyimides, polyether imides, poly(meth)acrylate,polyurethane, polyvinyl compounds, polystyrenes, polyoxymethylene orpoly(para-dioxanone). Introduction of hydrolysable groups, such asdiglycolide, dilactide, polyanhydrides or polyorthoesters can producebiodegradable triple-shape-memory polymers [Lendlein, A. & Langer, R.:Biodegradable, elastic shape-memory polymers for potential biomedicalapplications. Science, 2002. 296(5573): p. 1673-1676, Lendlein, A. &Kelch, S.: Degradable, Multifunctional Polymer Biomaterials withShape-memory. Materials Science Forum, 2005. 492-493: p. 219-224].

Polymer networks, which enable the triple-shape-memory effect, can beconfigured as AB-networks, where both chain segments contribute to theelasticity or as side chain networks, where the segments between thecross-linking sites predominantly contribute to the elasticity. Thefirst may be realized, for example, by the polymerization ofpoly(ε-caprolactone)dimethacrylate with cyclohexylmethacrylate (MACL). Aside chain network can be realized by the polymerization ofpoly(ε-caprolactone)dimethacrylate with polyethylene glycolmonomethylether methacrylate (CLEG). Both network architectures aregraphically illustrated in FIG. 1; (1) indicates here PCI-IMA segments;(2) PCL segments; (3) PEG side chains; and (4) cross-linking sites.

For programming purposes, segment of the test samples must be broughtinto a temporary form. The following exemplary methods may be used forprogramming:

-   -   Temporarily increasing the temperature above the switching        temperature(s) T_(switch) with subsequent deformation    -   Temporarily introducing plasticizers, so that the ambient        temperature is above T_(switch), with a subsequent deformation        and removal of the plasticizer.

Programming of a different segments of the component must here beperformed separately for each segment of the component, whereby care hasto be taken that the programming of a particular segment does not cancelthe programming of another segment. The programming is done independence of the switching temperature. This means that in practice thesegment with the highest T_(switch) is programmed first, whereafter thetemperature is sequentially lowered, followed by programming ofadditional segments. In addition, different programming methods can beused for individual segments.

For retrieving the two shape changes of the component, the componentmust be moved into the heat-transmitting medium, wherein the temperatureof the medium is successively increased, until the first shape changeoccurs. The additional shape change of the component occurs only whenthe temperature of the medium is increased further.

The principle of the triple-shape-memory polymers (or triple-shapepolymers) has already been described in detail. Known segments are herebased, on one hand, on the combination of segments made of polyethyleneglycol (PEG) and poly(ε-caprolactone) (PCL) and, on the other hand, onthe combination of PCL and cyclohexyl methacrylate (CHMA). The switchingtemperatures for using the triple-shape-memory effect are in the firstcase at 40 and 70° C. and in the second case at 70 and 130° C. In bothcases, the shape change of components made from different materialclasses can only be stimulated through heat conduction of the air andhence takes a long time (40 to 80 minutes). Water is a very good heattransfer medium, but is not available for either polymer system, becauseit causes in PEG/PCL system swelling of the network due to thehydrophilic characteristic of PEG. Crystalline PEG regions may alsoswell, thereby negating the physical cross-linking required for thetriple-shape-memory effect. In the PCL/CHMA system, water cannot beheated to the required switching temperature of 130° C. under normalpressure. Several applications, for example in the medical field,require complex shape changes, in particular those which includes asequential order of the shapes A→B→C, sometimes within very short timeintervals. It may for example be necessary to reshape a “round” tubeinto an “oval” tube and then back into a “round” tube. Until now, noneof the aforedescribed triple-shape-memory polymers can produce thisdeformation in an aqueous environment. The shape changes attainable sofar are limited by the programmable shapes, a movement of the testsample is so far only feasible to the extent to which this shape changehas previously been programmed. In particular, two-dimensional orthree-dimensional movements are severely limited. An additionaldisadvantage of the conventional systems is their low elasticity, inparticular below the switching temperature.

The conventional systems have therefore the following disadvantages:

-   -   Until now, the use of the one-way shape-memory effect allows        only a one-time change of a shape by thermal stimulation. The        change of the stimulation conditions, for example an additional        increase of the temperature, has no effect on to the shape of a        component, if T_(perm) is not exceeded, which would cause        melting of the component with thermoplastics.    -   With the introduction of the triple-shape-memory polymers, it        becomes possible to realize all together three different shapes        of the component. The successive stimulation of the individual        shapes is attained by a temperature increase after suitable        programming of the component. However, programming of known        triple-shape-memory polymers is very demanding.    -   The material should provide high elasticity, i.e., high        elongation at break, in particular greater than 400% at room        temperature. However, known triple-shape-memory polymers have        significantly lower elasticity.    -   Known triple-shape-memory polymers are sensitive to water, so        that water is eliminated as a particularly effective heat        transfer medium. The swelling properties and switching        temperatures do not allow a shape change in water.

The aforementioned problems have so far not been solved, although therecently introduced concept of triple-shape-memory polymers has openedthe possibility for sequential control of the thermally inducedshape-memory effect. Neither a one-step programming of thetriple-shape-memory effect at room temperature, nor a high elongation atbreak >400%, nor a variation of the trigger temperature throughselection of the programming temperature have been realized to date withtriple-shape-memory materials. It has also not been possible to date tomake the triple-shape-memory effect reversible, renewed programming hasso far been required after each shape recovery.

It is therefore an object of the invention to solve or at leastalleviate one or more of the aforementioned problems.

SUMMARY OF THE INVENTION

A first aspect of the invention is to provide a polymer network withtriple-shape-memory effect. The polymer network includes

A) a first crystalline switching segment made of a star polymer; and

B) a second crystalline switching segment made of a linear polymer or astar polymer.

In the present context, star polymers are defined as polymers with atleast three linear side arms, connected to a central core. In otherwords, the term star polymer relates to polymers with a primary chainand at least one long chain branch or polymers with several long chainbranches which are attached at a common branch point on the primarychain. Preferably, these are polymers with a total of three or four sidearms.

The two crystalline switching segments are covalently bonded with eachother in the polymer network. The triple-shape-memory materialsaccording to the invention are therefore composed of at least twodifferent macro-monomers. At least one macro-monomer must hereby be astar-shaped telechelic molecule, which has at least three side arms,each having a reactive end group. The second macro-monomer must belinear with at least two reactive end groups, or the two macro-monomersare star-shaped telechelic molecules. In addition, both phases must becrystalline. The triple-shape-memory material can be a multi-phasesystem, in which at least two phases are crystalline.

Preferably, the first crystalline switching segment is comprised of astar polymer based on poly(pentadecalactone) (PPDL segment).Independently, but more particularly in combination, the secondcrystalline switching segment may be comprised of a star polymer basedon poly(ε-caprolactone) (PCL segment) or polytetrahydrofurane (PTHFsegment).

In addition, in particular in combination with the aforementionedparticular embodiments, polymer networks are preferred where the meltingpoints of the two crystalline switching segments are in a range of 0° C.to 100° C., in particular in a range from room temperature to 100° C.Preferably, the melting points of the two crystalline switching segmentsare separated by at least 15° C., in particular by at least 20° C.

According to another preferred embodiment, the first crystallineswitching segment and/or the second crystalline switching segment of thepolymer network has an average molecular weight in a range from 500 to50,000 g/mole, in particular in a range from 1000 to 5000 g/mole. Thesesegments have a molecular weight in the aforementioned rangeparticularly in polymer networks with PPDL, PCL or PTHF segments.

Preferably, the fraction of individual switching segments, in particularof the PPDL segments, as part of the total weight of all crystallineswitching segments is 20 to 80 wt.-%. In particular, the fraction of thePPDL segments as part of the total weight of a polymer network with PPDLsegments and PCL segments is 20 to 80 wt.-%.

The triple-shape material may be produced, for example, by synthesizingas a first intermediate product a star polymer based onpoly(pentadecalactone) with functional end (terminal) groups arranged onthe side arms (this preliminary stage can also be referred to as anonlinear telechelic molecule with three or more arms). An importantfirst intermediate product in the synthesis of the triple-shape-memorymaterial is therefore in particular a star polymer based onpoly(pentadecalactone) with a respective terminal functional group oneach side arm. This star polymer based on poly(pentadecalactone) haspreferably an average molecular weight in a range from 500 to 50,000g/mole, in particular in a range from 1000 to 5000 g/mole. Basically,three methods are available for synthesizing the star polymers: (i)connecting prefabricated arms with a core, (ii) polymerization from amulti-functional initiator, and (iii) a combination of these twomethods.

As a second intermediate product a linear polymer or a star polymer, forexample based on poly(ε-caprolactone) or polytetrahydrofurane withlikewise functional end groups arranged on the side arms, is used. Thissecond polymer intermediate product has preferably an average molecularweight in a range from 500 to 50,000 g/mole, in particular in a rangefrom 1000 to 25,000 g/mole.

The two polymer intermediate products are covalently linked via theirterminal functional groups. The linkage can be either direct or viasuitable coupling reagents (for example diisocyanates). Moreparticularly, the linkage can also occur by a polyaddition reaction orthrough photopolymerization. Preferably, the functional group is ahydroxyl, acrylate or methacrylate group.

The invention offers, inter alia, the following advantages:

-   a. PPDL-based networks have a triple-shape-memory functionality,    which can be programmed at room temperature through cold stretching.-   b. By using water as heat transfer medium, triple-shape-memory    polymers can attain the temperatures required for shape changes    significantly more quickly than by using air as heat transfer    medium.-   c. By selecting a second switching segment which has a transition    temperature below the boiling temperature of water and is insoluble    in water, heat can now be transferred using water.-   d. The permanent shape in the polymer networks according to the    invention is formed already during the polymerization. The network    formation can here occur in particular through polymerization of    methacryl groups as well as through polycondensation of hydroxyl    groups with diisocyanates. The polymerization can be either    thermally initiated or photochemical. In particular, the    photochemical polymerization enables bodies with complex shapes,    because it is not performed from solution.-   e. PPDL-based networks, unlike the aforedescribed    triple-shape-memory networks, have significantly greater elasticity    and are also not soluble/swellable in water.-   f. Elongation fixation ratios and elongation recovery ratios have    values above 90%.-   g. Layers of the polymer networks can be differently programmed in    one dimension and are capable of realizing many three-dimensional    movements after being glued together covalently as a multilayer    system.-   h. The networks show under constant tension a thermally induced    reversible triple-shape-memory effect. High elongations of 100% and    more can be attained. This triple-shape-memory effect can be    reproduced without reprogramming as long as the sample is under    tension.

By using star-shaped PPDL oligomers, a network architecture is formedwhich due to the selection of the switching temperature has superiormechanical properties, such as elasticity, cold stretching ability andthe selection of the trigger temperature, compared to the conventionalsystems. PPDL has always been used in conventional shape-memory networksas a hard segment. This is the first use of PPDL segments as switchingsegment. It is also the first triple-shape-memory network architecturein which two crystalline primary chain segments are used whichcontribute to the overall elasticity of the network. The structure ofmultilayer systems enables a significant broadening of possible shapechanges, thus significantly enlarging the spectrum of applications forthe polymers.

Components produced from a uniform triple-shape-memory polymer can beintentionally switched with a time offset by increasing the ambienttemperature in an aqueous environment. With the one-step programming oftriple-shape-memory networks with a crystalline and a glassy segment,recovery of the programming after a certain time has been observed.Triple-shape-memory networks with two crystalline segments, wherein bothcrystalline phases contribute to the total elasticity, do not exhibitthis undesirable recovery.

By using triple-shape-memory polymers with several switching segments,two consecutive shape transitions can be realized in a polymer.

Additional Aspects of the Invention are:

-   A) New approaches for network synthesis    -   1. The networks are built from two different star-shaped        telechelic molecules, or    -   2. The networks are built from a star-shaped telechelic molecule        and a linear telechelic molecule.-   B) PPDL segments are used for the networks    -   1. PPDL is insoluble in water    -   2. PPDL has a melting temperature below 100° C.-   C) PPDL-based shape-memory systems have high elasticity    -   1. PPDL-based shape-memory systems allow programming by cold        stretching    -   2. PPDL-based shape-memory systems allow a noticeable increase        in elongation when crystallizing under tension-   D) PCL and PPDL segments are covalently cross-linked    -   1. The network architecture allows the creation of a temperature        shape-memory effect over a wide temperature range (room        temperature to T_(m,PPDL)).

The polymer network based on star-shaped segments ofpoly(pentadecadolactone) (PPDL) can perform several shape change steps.These are characterized by the following aspects

(1) High elasticity at room temperature (RT)

(2) The triple-shape-memory effect can be programmed at ambienttemperature (T<T_(m,PPDL)) by cold stretching

(3) Programming can be performed as one-step programming.

Combinations are possible which allow a temperature shape-memory effectfor one of the two switching faces. A multilayer architecture of samplebodies allows complex three-dimensional shape changes. Combinations arealso possible which show a reversible triple-shape-memory effect afterpre-stretching under constant tension.

According to another aspect of the invention, a method is provided forprogramming a polymer network with triple-shape-memory effect of theaforedescribed composition. The programming method includes the step of:

Programming of at least two different shapes of the polymer network with

-   -   a) A two-step method;    -   b) A one-step method;    -   c) Cold stretching;    -   d) A combination of heating and cold stretching; or    -   e) Preconditioning by stretching.

In particular, programming can be performed according to the two-stepmethod, wherein the polymer network is heated to T_(high) above the twomelting temperatures T_(m,1) and T_(m,2) of the crystalline switchingsegments (T_(m,1)<T_(m,2)), deformed, cooled to a temperature belowT_(m,2), deformed again, and then cooled to a temperature T_(m,1).

Programming can also be performed according to the one-step method,wherein the polymer network is heated to T_(high) above the two meltingtemperatures T_(m,1) and T_(m,2) of the crystalline switching segments<T_(m,2)), deformed and then cooled to a temperature below T_(m,1). Therecovery occurs during heating to T_(high). First, a recovery occurs atT_(sw,1), and then upon further heating at T_(sw,2).

Programming can also be performed by cold stretching, wherein thepolymer network is deformed at a temperature T_(low) below the twomelting temperatures T_(m,1) and T_(m,2) of the crystalline switchingsegments (T_(low)<<T_(m,1)<T_(m,2)). The recovery occurs during heatingto T_(high). First, a recovery occurs at T_(sw,1) and then upon furtherheating at T_(sw,2).

Programming can also be performed by a combination of heating and coldstretching, wherein the polymer network is deformed at a temperatureT_(mid) which is between the two melting temperatures T_(m,1) andT_(m,2) of the crystalline switching segments (T_(m,1)<T_(mid)<T_(m,2)).The recovery occurs during heating to T_(high). First, a recovery occursat T_(sw,1), and thereafter upon further heating at T_(sw,2).

Programming can also be performed with preconditioning by stretching atT_(high). If the tension is kept constant even after stretching, thentwo shapes are stepwise attained by expansion when cooling to T_(low),which are characterized by the two crystallization temperatures T_(c,1)and T_(c,2) (T_(high)>T_(c,1)>T_(c,2)>T_(low)), allowing reversibleswitching between three shapes. The extent of stretching herebydetermines the deformation during cooling. The recovery occurs duringheating to T_(high) under constant tension. Initially, there is arecovery at T_(sw,1) and upon further heating at T_(sw,2). Switchingbetween the shapes by cooling and heating can be arbitrarily repeatedunder constant tension, without requiring an additional programmingstep.

The recovery can take place under tension or by heating without tensionacross both T_(sw). In particular, this can take place in water. Anotheraspect of the invention therefore relates to a method for recovering aprogrammed polymer network with triple-shape-memory effect, whichincludes step of thermal treatment of the programmed polymer network inwater as thermal medium.

By selecting the programming temperature, the switching temperature of ashape-memory transition in the melting region of the two crystallinephases can be arbitrarily set.

Preferably, several layers of the polymer networks are joined with oneanother. The layers can be programmed identically or may have differentmagnitude, direction or programming temperature. Accordingly, tensiongradients of different magnitude and direction can thus be generated inthe multilayer material at different T_(switch), which can result incomplex shape changes.

If thin layers of the triple-shape-memory polymer, which have beensubjected to different programming with respect to magnitude ordirection, are covalently glued together, then this multilayer testsample can perform highly complex movements when the shape-memory effectis activated.

For realizing complex three-dimensional shape changes, onlyone-dimensional programming steps are required for the polymer layerswhich are then joined according to a calculated architecture. In thisway, shapes can be attained which are difficult or impossible whenprogrammed on bulk test samples. The attainable shapes are furtheraugmented by using triple-shape-memory materials.

If tension is maintained in one or several layers that have been gluedtogether from previously programmed layers, then the complexthree-dimensional shape changes are completely or partially reversible.

Another aspect of the invention therefore relates to a method forproducing layer systems from polymer shape-memory materials with thesteps:

-   a) Providing at least two layers made of polymer shape-memory    materials; and-   b) Producing a layer system from the at least two layers by reactive    gluing, wherein the two layers differ with respect to their    programming, shape or composition.

The layers can be provided in planar form or with a three-dimensionalprofile. The layers can have a different layer thickness. The layers mayalso consist of a polymer matrix with integrated shape-memory polymerfibers. The layers can also have different degrees of programming, inparticular degrees of stretching, and/or a different programmingorientation. Lastly, the layers can be programmed mono-directionally ormulti-directionally.

Other preferred embodiments of the invention are recited as additionalfeatures in the dependent claims.

Exemplary embodiments of the invention will now be described withreference to the appended drawings. These show in:

FIG. 1 conventional polymer network architectures, namely (a) a MACLnetwork and (b) a CLEG network;

FIG. 2A a network architecture of a system according to the inventionand its representation according to a first embodiment;

FIG. 2B a network architecture of a system according to the inventionand its representation according to a second embodiment;

FIGS. 3 to 5 layer systems made of polymer shape-memory materials indifferent variants; and

FIG. 6 reversible triple-shape-memory properties of the network a:T-PPDL(4)-PCL(8,50) at a tension of 0.6 MPa; b: T-PPDL(3)-PCL(8,50) at atension of 1 MPa.

The synthesis of the hydroxy-telechelic star polymers with PCL- orPPDL-side arms occurs through ring opening polymerization ofε-caprolactone or pentadecadolactone with tri- or tetra-functionalinitiators. The synthesis can occur according to the followingdescription: Arvanitoyannis, I., et al.: Novel Star-Shaped Polylactidewith Glycerol Using Stannous Octoate or Tetraphenyl Tin as Catalyst 1.Synthesis, Characterization and Study of Their Biodegradability,Polymer, 1995, 36(15), p. 2947-2956. However, in contrast to thisreference, the ring opening polymerization of PPDL was performed in 14to 21 days. Hydroxy-telechelic star polymers with PTHF side arms canalso be synthesized in an analogous manner.

Examples for structures of polymer networks made of star-shapedtelechelic molecules are illustrated in FIGS. 2A and 2B.

Synthesis of hydroxy-telechelic oligo(ε-caprolactone) PCL(x)-OH

97 ml ε-caprolactone, 0.68 g pentaerythrite and 280 mg dibutyltinoxide(DBTO) were reacted while stirring in a Schlenk flask in hydrogenatmosphere at 130° C. After a polymerization time of 7 h the reactionmixture is cooled to room temperature. The oligomers are dissolved in anapproximately sixfold volume excess of dichloromethane. The reactionproduct is precipitated by slowly dripping the solution into anapproximately tenfold volume excess of hexane fraction under strongstirring. The precipitate is washed with hexane fraction and dried at25° C. in vacuum (approximately 1 mbar) until attaining constant weight.The molar mass and functional groups as well as the thermal propertieswere analyzed by determining the OH-number, GPC, ¹H-NMR and DSC. TheOH-number determination yielded M_(n)=22,700 g mole⁻¹. DSC measurementsgave a melting temperature of 54.5° C., ΔH 76.8 J*g⁻¹. The obtainedoligo(ε-caprolactone) with M_(n) of about 20,000 g/mol will subsequentlybe referred to as PCL(20)-OH.

The synthesis of the hydroxy-telechelic oligo(ε-caprolactone)s PCL(4)-OHwith M_(n) 4000 g·mole⁻¹ or the hydroxy-telechelicoligo(ε-caprolactone)s PCL(8)-OH with M_(n) 8000 g·mole⁻¹ took place viaring opening polymerization of ε-caprolactone similar to PCL(20)-OH.PCL(8)-OH is also commercially available under the label CAPA4801.

Synthesis of hydroxyl-telechelic oligo(pentadecadolactone) PPDL(y)-OH

112.5 g pentadecadolactone, 3.375 g 1,1,1-tris(hydroxymethyl)ethane(optionally also other tri- or tetra-functional initiators) and DBTO 105mg were reacted while stirring in a Schlenk flask in a nitrogenatmosphere at 130° C. After a polymerization time of 7 h the reactionmixture is cooled to room temperature. The oligomers are dissolved in anapproximately sixfold volume excess of dichloromethane. The reactionproduct is precipitated by slowly dripping the solution into anapproximately tenfold volume excess of hexane fraction under strongstirring. The precipitate is washed with hexane fraction and dried at50° C. in vacuum (approximately 1 mbar) until attaining constant weight.

The molar mass and functional groups as well as the thermal propertieswere analyzed by determining the OH-number, GPC, ¹H-NMR and DSC. TheOH-number determination yielded M_(n)=4000 g mole⁻¹. DSC measurementsdetected two melting temperatures of 49.8° C. and 84.8° C., ΔH 109.5J·g⁻¹. The obtained oligo(pentadecadolactone) with M_(n) of about 4000g/mol will subsequently be referred to as PPDL(4)-OH.

The synthesis of the hydroxy-telechelic oligo(pentadecadolactone)sPPDL(3)-OH with M_(n) 3000 g·mole⁻¹ or of the hydroxy-telechelicoligo(pentadecadolactone)s PPDL(2)-OH with M_(n) 2000 g·mole⁻¹ wasperformed similar to the synthesis of PPDL(4)-OH.

Synthesis of oligo(ε-caprolactone)tetramethacrylate PCL(x)-IEMA

50.0 g PCL(20)-OH, 1.6 ml IEMA and 6.5 μL dibutyltin(IV)dilaurate weredissolved in 250 ml dichloromethane under argon and stirred at roomtemperature for 5 days. The reaction product is precipitated by slowlydripping the solution into an approximately tenfold volume excess ofhexane fraction under strong stirring. The precipitate is washed withhexane fraction and dried at 25° C. in vacuum (approximately 1 mbar)until attaining constant weight. ¹H-NMR showed that the OH-groups inPCL(20)-OH have completely reacted with IEMA. The obtainedoligo(ε-caprolactone)tetramethacrylate will subsequently be referred toas PCL(20)-IEMA.

The synthesis of the oligo(ε-caprolactone)tetramethacrylate PCL(4)-IEMAwith M_(n) 4000 g·mole⁻¹ and of theoligo(ε-caprolactone)tetramethacrylates PCL(8)-IEMA with M_(n) 8000g·mole⁻¹ was performed similar to PCL(20)-IEMA.

Synthesis oligo(pentadecadolactone)trimethacrylate PPDL(y)-IEMA

50.0 g PPDL(4)-OH, 6.1 ml IEMA and 25.4 μL dibutyltin(IV)dilaurate weredissolved in 250 ml dichloromethane under argon and stirred at roomtemperature for 5 days. The reaction product is precipitated by slowlydripping the solution into an approximately tenfold volume excess ofhexane fraction under strong stirring. The precipitate is washed withhexane fraction and dried at 25° C. in vacuum (approximately 1 mbar)until attaining constant weight. It was demonstrated with ¹H-NMR thatthe OH-groups in PPDL(4)-OH have completely reacted with IEMA. Theobtained oligo(pentadecadolactone)trimethacrylate will subsequently bereferred to as PPDL(4)-IEMA.

Synthesis of the Networks According to the Polycondensation Method A)

The produced star polymers PCL(x)-OH and PPDL(y)-OH were dissolved indichloromethane with a suitable mixing ratio. 2,2,4- and2,4,4-trimethylhexane-1,6-diisocyanate (TMDI) is added as cross-linker.Mixtures with 25-75 wt.-% PPDL(y)-OH have proven to be suitable mixingratios for triple-shape-memory polymers.

The hydroxy-telechelic oligomers are dissolved with an approximatelytenfold excess mass of dichloromethane under nitrogen. Diisocyanate isadded to the solution while stirring. The quantity of diisocyanatecorresponds here to a molar ratio of the isocyanate to hydroxyl groupsof 1.05 to 1.00. The calculation in Table 1 is based on the averagevalue of the molar mass of the hydroxyl functionality of the polymereducts determined by ¹H-NMR spectroscopy, for example of PPDL(4)-OH orPCL(20)-OH. The reaction mixture was stirred for five minutes at roomtemperature and filled into PTFE trays. Approximately 20 ml of thesolution are introduced when using trays with an inside diameter ofabout 100 mm. A continuous nitrogen flow is passed over the solutionsfor 24 h at 60° C. so as to carefully evaporate the solvent during thefilm formation. Thereafter, the films are heated under vacuum (about 100mbar) for 4 days to 80° C. The raw products of the poly-additionreactions are, unless otherwise stated, swollen in chloroform, thusdetermining the gel content and the degree of swelling, and dried at 80°C. in vacuum (1 mbar) until attaining constant weight. The weights ofthe oligomers and the diisocyanate and the gel content of the networksare listed in Table 1.

TABLE 1 Approaches for producing the networks from PCL(4)-OH, PCL(8)-OH,PCL(20)-OH, PPDL(2)-OH, PPDL(3)-OH, PPDL(4)-OH and TMDI according to thepolycondensation method A) (indicated by the prefix T); networkdesignation: PPDL(x)-PCL(y, z) are polymer networks made from thefollowing star-shaped pre-polymers: 3-arm PPDL with Mn about x · 1000g/mole and 4-arm PCL with M_(n) about y · 1000 g/mole and a fraction ofz mass-%; Degree of PPDL(y)- PCL(20)- PCL(8)- PCL(4)- swelling OH OH OHOH TMDI μ_(PPDL) Content in chloroform Designation (g) (g) (g) (g) (ml)(wt.-%) (wt.-%) (wt.-%) T-PPDL(4) 1.50 — — — 0.070 100 91 1420T-PPDL(4)- 0.75 2.25 — — 0.106 25 85 2220 PCL(20, 75) T-PPDL(4)- 1.2 1.8— — 0.113 40 85 1980 PCL(20, 60) T-PPDL(4)- 1.5 1.5 — — 0.118 50 88 1750PCL(20, 50) T-PPDL(4)- 1.8 1.2 — — 0.122 60 85 1960 PCL(20, 40)T-PPDL(4)- 2.25 0.75 — — 0.141 75 92 1440 PCL(20, 25) T-PPDL(4)- 0.75 —2.25 — 0.148 25 98 830 PCL(8, 75) T-PPDL(4)- 1.2 — 1.8 — 0.146 40 97 970PCL(8, 60) T-PPDL(4)- 1.5 — 1.5 — 0.145 50 95 1240 PCL(8, 50) T-PPDL(4)-1.8 — 1.2 — 0.144 60 92 1820 PCL(8, 40) T-PPDL(4)- 2.25 — 0.75 — 0.14375 92 1310 PCL(8, 25) T-PPDL(4)- 0.75 — — 2.25 0.26 25 97 1100 PCL(4,75) T-PPDL(4)- 1.2 — — 1.8 0.236 40 93 1350 PCL(4, 60) T-PPDL(4)- 1.5 —— 1.5 0.22 50 94 1360 PCL(4, 50) T-PPDL(4)- 1.8 — — 1.2 0.204 60 92 1280PCL(4, 40) T-PPDL(4)- 2.25 — — 0.75 0.18 75 94 1220 PCL(4, 25)T-PPDL(3)- 0.75 2.25 — — 0.106 25 85 2080 PCL(20, 75) T-PPDL(3)- 1.5 1.5— — 0.186 50 84 1940 PCL(20, 50) T-PPDL(3)- 2.25 0.75 — — 0.250 75 901250 PCL(20, 25) T-PPDL(3)- 0.75 — 2.25 — 0.200 25 98 800 PCL(8, 75)T-PPDL(3)- 1.5 — 1.5 — 0.238 50 97 790 PCL(8, 50) T-PPDL(3)- 2.25 — 0.75— 0.275 75 98 800 PCL(8, 25) T-PPDL(3)- 0.75 — — 2.25 0.302 25 95 1050PCL(4, 75) T-PPDL(3)- 1.5 — — 1.5 0.306 50 96 880 PCL(4, 50) T-PPDL(3)-2.25 — — 0.75 0.309 75 97 830 PCL(4, 25) T-PPDL(2)- 0.75 2.25 — — 0.13825 90 1620 PCL(20, 75) T-PPDL(2)- 1.5 1.5 — — 0.215 50 88 1710 PCL(20,50) T-PPDL(2)- 2.25 0.75 — — 0.293 75 95 1170 PCL(20, 25) T-PPDL(2)-0.75 — 2.25 — 0.214 25 98 800 PCL(8, 75) T-PPDL(2)- 1.5 — 1.5 — 0.66 5098 820 PCL(8, 50) T-PPDL(2)- 2.25 — 0.75 — 0.318 75 97 920 PCL(8, 25)T-PPDL(2)- 0.75 — — 2.25 0.317 25 96 1040 PCL(4, 75) T-PPDL(2)- 1.5 — —1.5 0.334 50 96 1030 PCL(4, 50) T-PPDL(2)- 2.25 — — 0.75 0.352 75 931100 PCL(4, 25)

Synthesis of the Networks with the Polymerization Method B)

The produced hydroxy-telechelic star polymers PCL(x)-IEMA orPPDL(y)-IEMA are melted and mixed, whereafter a thermal radicalinitiator (AIBN, BPO) is added. Here too, mixtures with 25-75 wt.-% PPDLhave been found to be suitable for triple-shape-memory polymer mixtures.Polymerization can alternatively also occur photochemically. Thefunctionalized oligomers are hereby melted, a 1 mole-% photo initiatoris added, the mixture is then mixed and photo-polymerized by irradiationwith a Hg-lamp.

TABLE 2 Approaches for preparing the networks from PCL(20)-IEMA andPPDL(4)-IEMA according to the polymerization method B) (indicated by theprefix P). Degree of PPDL(4)- PCL(8)- PCL(20)- swelling IEMA IEMA IEMAμ_(PPDL) Gel content in chloroform Designation (g) (g) (g) (wt.-%)(wt.-%) (wt.-%) P-PPDL(4)-PCL(20, 75) 0.75 — 2.25 25 87 840P-PPDL(4)-PCL(20, 60) 1.20 — 1.80 40 58 1660 P-PPDL(4)-PCL(20, 50) 1.50— 1.50 50 71 1050 P-PPDL(4)-PCL(20, 40) 1.80 — 1.20 60 54 1420P-PPDL(4)-PCL(20, 25) 2.25 — 0.75 75 78 1000 P-PPDL(4)-PCL(20, 12) 2.625— 0.375 88 87 650 P-PPDL(4)-PCL(8, 75) 0.75 2.25 — 25 88 620P-PPDL(4)-PCL(8, 60) 1.20 1.8 — 40 70 900 P-PPDL(4)-PCL(8, 50) 1.50 1.5— 50 87 590 P-PPDL(4)-PCL(8, 40) 1.80 1.2 — 60 65 980 P-PPDL(4)-PCL(8,25) 2.25 0.75 — 75 77 850Thermal Properties of the Polymer Networks

The networks from PPDL and PCL with M_(n) of 4000 g·mole⁻¹, 8000g·mole⁻¹ and 20,000 g·mole⁻¹ have in DSC experiments to melting rangesin a temperature region from −100° C. to 100° C. They can therefore beconsidered as semi-crystalline systems. Tables 3 shows the thermalproperties of the polymer networks. The two melting temperatures can beused as two T_(trans) for the triple-shape effect.

TABLES 3 Thermal properties of the polymer networks according to thepolycondensation method A) μ_(PPDL) T_(g) T_(m1) T_(m2) ΔH₁ ^(b))ΔH_(PCL) ^(c)) ΔH₂ ^(b)) ΔH_(PPDL) ^(c)) Designation [wt.-%] [° C.] [°C.] [° C.] [J · g⁻¹] [J · g⁻¹] [J · g⁻¹] [J · g⁻¹] T-PPDL(4) 100 n.d. —79.4 — — 99.4 99.4 T-PPDL(4)-PCL(20, 75) 25 n.d. 55.1 74.8 56.0 74.720.5 82.0 T-PPDL(4)-PCL(20, 60) 40 n.d. 54.3 76.9 40.6 67.7 30.7 76.8T-PPDL(4)-PCL(20, 50) 50 n.d. 52.6 77.1 29.4 58.8 40.2 80.4T-PPDL(4)-PCL(20, 40) 60 n.d. 53.5 79.1 32.8 82.0 53.3 88.8T-PPDL(4)-PCL(20, 25) 75 n.d. 52.0 78.6 18.8 75.2 64.0 85.3T-PPDL(4)-PCL(8, 75) 25 −54.6 36.9 72.5 39.0 52.0 21.3 85.2T-PPDL(4)-PCL(8, 60) 40 −55.2 38.6 74.2 33.9 56.5 29.9 74.8T-PPDL(4)-PCL(8, 50) 50 n.d. 39.9 77.5 30.4 60.8 44.0 88.0T-PPDL(4)-PCL(8, 40) 60 n.d. 42.3 79.1 25.4 63.5 51.9 86.5T-PPDL(4)-PCL(8, 25) 75 n.d. 42.8 79.5 17.6 70.4 71.1 94.8T-PPDL(4)-PCL(4, 75) 25 −47.8 31.0 71.7 34.0 45.3 19.2 76.8T-PPDL(4)-PCL(4, 60) 40 n.d. 34.5 77.1 33.7 56.2 34.7 86.8T-PPDL(4)-PCL(4, 50) 50 n.d. 33.1 75.1 24.0 48.0 46.2 92.4T-PPDL(4)-PCL(4, 40) 60 n.d. 31.9 75.3 18.3 45.3 55.8 93.0T-PPDL(4)-PCL(4, 25) 75 n.d. n.d. 78.7 n.d. n.d. 66.4 88.5T-PPDL(3)-PCL(20, 75) 25 −57.5 56.4 71.6 53.9 71.9 15.1 60.4T-PPDL(3)-PCL(20, 50) 50 n.d. 54.0 73.4 40.6 81.2 36.8 73.6T-PPDL(3)-PCL(20, 25) 75 n.d. 53.9 74.6 30.2 120.8 53.4 71.2T-PPDL(3)-PCL(8, 75) 25 −53.0 36.2 65.5 38.8 51.1 14.0 56.0T-PPDL(3)-PCL(8, 50) 50 n.d. 32.7 61.6 28.6 57.2 39.4 78.8T-PPDL(3)-PCL(8, 25) 75 n.d. 32.8 73.4 14.6 58.4 59.9 79.9T-PPDL(3)-PCL(4, 75) 25 −46.4 29.8 67.3 36.8 49.1 16.9 67.6T-PPDL(3)-PCL(4, 50) 50 n.d. 27.1 72.0 24.6 49.2 40.5 81.0T-PPDL(3)-PCL(4, 25) 75 n.d. n.d. 68.7 — — 70.6 70.6 T-PPDL(2)-PCL(20,75) 25 n.d. 55.0 n.d. 66.1 66.1 — — T-PPDL(2)-PCL(20, 50) 50 n.d. 54.264.5 49.8 99.6 22.8 45.6 T-PPDL(2)-PCL(20, 25) 75 n.d. n.d. 61.6 — —67.4 67.4 T-PPDL(2)-PCL(8, 75) 25 −51.4 35.0 53.7 45.2 60.3  6.3 25.2T-PPDL(2)-PCL(8, 50) 50 n.d. 31.3 54.0 30.4 60.8 23.6 47.2T-PPDL(2)-PCL(8, 25) 75 n.d. n.d. 58.4 — — 63.0 63.0 T-PPDL(2)-PCL(4,75) 25 −45.2 27.7 52.8 40.6 54.1 11.1 44.4 T-PPDL(2)-PCL(4, 50) 50 n.d.28.3 57.7 18.7 37.4 27.7 55.4 T-PPDL(2)-PCL(4, 25) 75 n.d. n.d. 63.5 — —65.7 65.7

TABLE 4 Thermal properties of the polymer networks according to thepolymerization method B) μ_(PPDL) T_(m1) T_(m2) ΔH₁ ΔH₂ Designationwt.-% ° C. ° C. J/g J/g P-PPDL(4)-PCL(20, 75) 25 47.0 68.6 50.7 15.0P-PPDL(4)-PCL(20, 60) 40 54.1 67.9/83.5 46.5 27.6 P-PPDL(4)-PCL(20, 50)50 53.7 70.0/83.8 32.6 46.1 P-PPDL(4)-PCL(20, 40) 60 54.1 74.1/84.3 20.363.0 P-PPDL(4)-PCL(20, 25) 75 52.9 81.7 22.7 47.1 P-PPDL(4)-PCL(20, 12)88 51.8 87.7 19.5 53.8 P-PPDL(4)-PCL(8, 75) 25 43.3 67.9 14.3 30.6P-PPDL(4)-PCL(8, 60) 40 47.2 71.7/81.5 24.8 51.9 P-PPDL(4)-PCL(8, 50) 5020.9 67.9 16.7 38.0 P-PPDL(4)-PCL(8, 40) 60 46.5 70.4 — 66.9P-PPDL(4)-PCL(8, 25) 75 46.4 73.0/82.2 16.1 74.8Mechanical Properties of the Polymer Networks

The mechanical properties of the networks are determined at 25° C., 60°C. and 100° C. by performing tensile tests. Whereas semi-crystallinematerials are present at 25° C., the networks are in a rubber-elasticstate at 100° C. Both temperature ranges are relevant for an applicationas shape-memory material, because they determine below T_(trans) themechanical properties of the test sample in the permanent and temporaryshape before programming and before completed recovery. However, themechanical properties above T_(trans) are important with regard toprogramming of the temporary shape. With tensile tests at 60° C., themechanical properties of the materials are also measured at thetemperature which is to be selected for programming the second shape.

At 25° C., the mechanical properties are determined by the glassy stateof the materials. The networks from PPDL, PCL and TMDI show in tensiletests a yield point accompanied by constriction of the sample.

The E-modules E have values between 134 MPa and 430 MPa. The tensilestrength σ_(max) is in a range from 15 MPa to 31 MPa at elongationsε_(max) of 6% to 16%. The observed average values for the elongation atbreak ε_(b) are between 400% and 1000%. The mechanical characteristicsof the investigated networks according to the poly-condensation methodA) are listed in Table 5.

TABLE 5 Mechanical properties of the polymer networks according topoly-condensation method A at 25° C., 60° C. and 100° C. μ_(PPDL) 25° C.60° C. 100° C. [wt E σ_(b) ε_(b) E σ_(b) ε_(b) E σ_(b) ε_(b) Designation%] [MPa] [MPa] [%] [MPa] [MPa] [%] [MPa] [MPa] [%] T-PPDL(4) 100 370 ±87 20.9 ± 2.6 523 ± 35 102 ± 16  9.9 ± 1.2 690 ± 54 0.65 ± 0.13 1.25 ±0.21 561 ± 68 T-PPDL(4)-PCL(20, 75) 25 273 ± 20 29.5 ± 2.3 717 ± 22 15.8± 1.3  4.8 ± 0.7 441 ± 26 1.84 ± 0.28 1.33 ± 0.12 171 ± 43T-PPDL(4)-PCL(20, 60) 40 332 ± 24 24.6 ± 3.9 621 ± 86 22.4 ± 3.3  6.8 ±1.4 484 ± 38 2.16 ± 0.30 1.80 ± 0.20 254 ± 45 T-PPDL(4)-PCL(20, 50) 50319 ± 16 30.4 ± 3.5 715 ± 43 28.9 ± 2.6  6.3 ± 0.9 463 ± 24 1.88 ± 0.261.91 ± 0.16 199 ± 21 T-PPDL(4)-PCL(20, 40) 60 272 ± 20 28.5 ± 4.7 692 ±59 23.3 ± 4.1  12.5 ± 2.6  588 ± 47 2.08 ± 0.60 1.18 ± 0.28 117 ± 7 T-PPDL(4)-PCL(20, 25) 75 300 ± 15 32.4 ± 4.2 664 ± 59 35.1 ± 3.0  8.2 ±0.8 489 ± 22 2.36 ± 0.22 1.43 ± 0.22 151 ± 30 T-PPDL(4)-PCL(8, 75) 25101 ± 16 20.3 ± 4.0 587 ± 49 8.0 ± 0.7 5.0 ± 0.8 292 ± 48 3.75 ± 0.352.12 ± 0.31 126 ± 20 T-PPDL(4)-PCL(8, 60) 40 185 ± 18 27.8 ± 4.3 665 ±59 7.3 ± 1.3 6.1 ± 0.7 471 ± 30 3.25 ± 0.08 1.92 ± 0.23 159 ± 41T-PPDL(4)-PCL(8, 50) 50 207 ± 18 23.6 ± 2.6 764 ± 29 12.7 ± 2.5  7.5 ±0.9 616 ± 23 2.41 ± 0.31 1.23 ± 0.25 103 ± 18 T-PPDL(4)-PCL(8, 40) 60257 ± 49 24.8 ± 3.5 707 ± 85 21.1 ± 6.7  6.3 ± 2.0 549 ± 43 1.97 ± 0.201.33 ± 0.13 206 ± 54 T-PPDL(4)-PCL(8, 25) 75 340 ± 33 25.8 ± 2.5 693 ±46 45.8 ± 8.4  9.1 ± 1.1 557 ± 62 1.79 ± 0.12 1.22 ± 0.18 230 ± 52T-PPDL(4)-PCL(4, 75) 25  73 ± 15 20.5 ± 2.0 673 ± 28 6.7 ± 0.9 2.9 ± 0.6151 ± 40 3.38 ± 0.26 1.33 ± 0.10  65 ± 10 T-PPDL(4)-PCL(4, 60) 40 179 ±17 27.1 ± 2.5 714 ± 27 16.1 ± 5.8  3.4 ± 0.5 228 ± 39 2.98 ± 0.11 1.54 ±0.07 103 ± 9  T-PPDL(4)-PCL(4, 50) 50 131 ± 21 21.2 ± 3.4 486 ± 42 18.2± 3.8  4.3 ± 1.0 263 ± 37 2.53 ± 0.21 1.80 ± 0.14 206 ± 40T-PPDL(4)-PCL(4, 40) 60 154 ± 10 24.9 ± 1.9 562 ± 32 34.1 ± 7.0  7.5 ±1.9 346 ± 40 2.23 ± 0.12 1.33 ± 0.16 155 ± 30 T-PPDL(4)-PCL(4, 25) 75274 ± 22 25.3 ± 3.9 691 ± 57 59.8 ± 6.2  8.9 ± 0.7 521 ± 39 1.47 ± 0.131.01 ± 0.16 188 ± 48 T-PPDL(3)-PCL(20, 75) 25 305 ± 43 25.2 ± 3.5 691 ±51 2.3 ± 0.2 2.3 ± 0.3 457 ± 50 0.87 ± 0.07 0.95 ± 0.13 286 ± 62T-PPDL(3)-PCL(20, 50) 50 282 ± 21 19.7 ± 2.7 543 ± 36 10.5 ± 0.9  3.8 ±0.2 461 ± 19 0.92 ± 0.02 0.83 ± 0.06 235 ± 23 T-PPDL(3)-PCL(20, 25) 75242 ± 23 31.2 ± 5.0 595 ± 53 20.7 ± 1.9  8.4 ± 1.3 503 ± 39 1.79 ± 0.101.20 ± 0.10 146 ± 22 T-PPDL(3)-PCL(8, 75) 25 37 ± 7 11.0 ± 2.9 425 ± 994.3 ± 0.3 2.3 ± 0.2 140 ± 24 4.82 ± 0.19 1.72 ± 0.35  57 ± 17T-PPDL(3)-PCL(8, 50) 50  64 ± 12 15.9 ± 1.9 433 ± 26 9.9 ± 0.6 4.4 ± 0.5226 ± 32 4.29 ± 0.19 1.62 ± 0.23  62 ± 17 T-PPDL(3)-PCL(8, 25) 75  97 ±13 23.7 ± 2.3 437 ± 23 3.9 ± 0.1 5.9 ± 0.9 260 ± 46 3.70 ± 0.10 1.82 ±0.19  92 ± 16 T-PPDL(3)-PCL(4, 75) 25 58 ± 9 20.8 ± 4.5 525 ± 48 3.0 ±0.4 1.7 ± 0.2 140 ± 36 2.60 ± 0.11 1.07 ± 0.16  67 ± 15 T-PPDL(3)-PCL(4,50) 50  67 ± 10 18.6 ± 3.5 423 ± 57 12.9 ± 1.5  4.6 ± 0.7 164 ± 43 3.40± 0.12 1.47 ± 0.11 69 ± 9 T-PPDL(3)-PCL(4, 25) 75  84 ± 11 23.4 ± 6.9405 ± 47 19.7 ± 1.3  6.1 ± 0.4 195 ± 11 3.75 ± 0.11 1.67 ± 0.38  83 ± 30T-PPDL(2)-PCL(20, 75) 25 178 ± 55 17.2 ± 5.5 684 ± 91 1.5 ± 0.2 2.0 ±0.4 521 ± 68 1.44 ± 0.07 1.04 ± 0.20 188 ± 64 T-PPDL(2)-PCL(20, 50) 50206 ± 12 24.4 ± 3.2 784 ± 52 4.3 ± 0.9 3.7 ± 0.5 614 ± 51 1.28 ± 0.070.97 ± 0.09 207 ± 36 T-PPDL(2)-PCL(20, 25) 75 134 ± 10 26.6 ± 4.4 649 ±20 5.7 ± 1.9 4.7 ± 1.1 463 ± 34 2.28 ± 0.08 1.16 ± 0.15 110 ± 30T-PPDL(2)-PCL(8, 75) 25 23 ± 4  9.7 ± 1.4 384 ± 49 4.0 ± 0.1 2.0 ± 0.4107 ± 35 4.74 ± 0.29 1.36 ± 0.36  42 ± 20 T-PPDL(2)-PCL(8, 50) 50  52 ±12 13.6 ± 2.5 459 ± 70 3.4 ± 0.2 2.0 ± 0.5 141 ± 58 4.03 ± 0.17 1.53 ±0.34  66 ± 22 T-PPDL(2)-PCL(8, 25) 75  76 ± 10 24.0 ± 6.2 605 ± 34 3.1 ±0.2 2.7 ± 0.6 270 ± 68 3.18 ± 0.21 1.33 ± 0.23  71 ± 18 T-PPDL(2)-PCL(4,75) 25  18 ± 12 15.8 ± 3.6 502 ± 31 2.6 ± 0.2 1.5 ± 0.4 110 ± 42 2.68 ±0.06 1.11 ± 0.13  67 ± 13 T-PPDL(2)-PCL(4, 50) 50 15 ± 3 19.1 ± 3.1 606± 23 3.1 ± 0.3 1.9 ± 0.2 161 ± 21 2.84 ± 0.05 1.07 ± 0.19  59 ± 18T-PPDL(2)-PCL(4, 25) 75  65 ± 17 21.8 ± 3.1 616 ± 67 3.6 ± 0.5 3.8 ± 0.4396 ± 44 1.99 ± 0.07 0.92 ± 0.11  76 ± 16

TABLE 6 Mechanical properties of the polymer networks according topolymerization method B) 25° C. 60° C. 100° C. μ_(PPDL) E σ_(b) ε_(b) Eσ_(b) ε_(b) E σ_(b) ε_(b) Designation [wt %] [MPa] [MPa] [%] [MPa] [MPa][%] [MPa] [MPa] [%] P-PPDL(4)-PCL(20, 75) 25 245 ± 5  17.2 ± 4.4  160 ±84  3.7 ± 0.4 3.8 ± 0.6 180 ± 25  2.03 ± 0.39 1.41 ± 0.51 90 ± 20P-PPDL(4)-PCL(20, 60) 40 270 ± 18 9.7 ± 0.7 4.3 ± 0.5 6.1 ± 0.4 1.1 ±0.2 70 ± 12 1.54 ± 0.20 0.70 ± 0.04 60 ± 10 P-PPDL(4)-PCL(20, 50) 50 200± 10 12.8 ± 0.8   11 ± 1.7 10.1 ± 6.7  1.2 ± 0.3 30 ± 15 1.25 ± 0.050.79 ± 0.18 80 ± 14 P-PPDL(4)-PCL(20, 40) 60 289 ± 34 8.0 ± 1.0 3.3 ±0.6 6.8 ± 2.9 1.0 ± 0.1 40 ± 39 1.58 ± 0.56 0.60 ± 0.37 45 ± 22P-PPDL(4)-PCL(20, 25) 75 273 ± 11 11.7 ± 0.65 28 ± 11 26.0 ± 2.1  2.5 ±2.9 30 ± 8  2.19 ± 0.17 1.06 ± 0.03 65 ± 2  P-PPDL(4)-PCL(20, 12) 88 121± 4  8.2 ± 0.4 60 ± 11 22.8 ± 4.8  2.7 ± 0.4 23 ± 10 3.62 ± 0.64 1.24 ±0.68 52 ± 15 P-PPDL(4)-PCL(8, 75) 25  121 ± 4.2 8.3 ± 3.7 63 ± 11 6.69 ±1.68 1.5 ± 0.8 48 ± 14 4.46 ± 1.12 1.43 ± 0.55 44 ± 2  P-PPDL(4)-PCL(8,60) 40 181 ± 15 8.8 ± 1.0 25 ± 30 9.56 ± 6.23 1.3 ± 0.6 20 ± 3  2.52 ±0.58 0.56 ± 0.50 30 ± 20 P-PPDL(4)-PCL(8, 50) 50 126 ± 30 9.9 ± 1.6 90 ±24 11.7 ± 1.02 2.6 ± 0.4 46 ± 12 4.69 ± 0.29 1.53 ± 0.58 40 ± 13P-PPDL(4)-PCL(8, 40) 60 241 ± 10 7.0 ± 1.4 4 ± 1 21.4 ± 4.4  1.2 ± 0.3 9± 4 1.89 ± 0.16 0.62 ± 0.03 42 ± 7  P-PPDL(4)-PCL(8, 25) 75 203 ± 25 9.4± 1.1 37 ± 38 23.9 ± 1.2  2.0 ± 0.2 18 ± 4  2.2 ± 0.3 0.45 ± 0.24 22 ±13

Triple-Shape-Memory Properties of the Polymer Networks Experiment A

In both synthesis methods (A and B), the permanent shape (1. shape) isfixed by the cross-linking. The first programming is performed (2.shape) by bending a sample end perpendicularly at 100° C. and subsequentcooling to 60° C. The second programming (3. shape) is performed byperpendicularly bending the second sample end at 60° C. and subsequentcooling to 0° C. When immersing a test sample programmed in this way ina water bath having a temperature of 60° C., the sample side with thelower T_(switch) (2. shape) is initially recovered. This processrequires that the switching temperature in the test sample is reachedand lasts only for several seconds. The other sample side remainsunchanged. The second sample side is also recovered to form an overallplanar body (1. shape) by increasing the temperature of the water bathor by immersing the sample in a second water bath at 100° C.

Experiment B

The triple-shape-memory effect is quantitatively investigated by cyclicthermo-mechanical tensile tests, as described in Bellin et al. (seeabove). The shape-memory properties of the networks of PPDL(y) andPCL(x) with varying molar mass, as determined by tension-controlled,cyclic thermo-mechanical tensile tests, are listed in Table 7. Theinvestigations show that these materials have stretch fixation andstretch return ratios of more than 90% in all cycles.

The employed polymers may be biostable or biodegradable. Multiblockcopolymers which have a switching temperature in the range of the humanbody temperature are known for medical applications.

TABLE 7 Triple-shape-memory properties of the polymer networks accordingto the poly-condensation method A. R_(f) and R_(r) are averaged valuesfrom the cycles 2 to 5. The switching temperatures are averaged valuesfrom all 5 cycles. R_(f)(C→B) R_(f)(B→A) R_(r)(A→B) R_(r)(A→C) T_(sw1)T_(sw2) Designation [%] [%] [%] [%] [° C.] [° C.] T-PPDL(4)-PCL(20, 75)74.5 ± 1.0 99.0 ± 0.1 56.2 ± 1.0 96.3 ± 7.0 66.0 ± 0.8 85.3 ± 1.1T-PPDL(4)-PCL(20, 60) 80.1 ± 0.5 98.2 ± 0.1 81.1 ± 0.7 101.0 ± 0.5  61.0± 0.5 84.4 ± 0.5 T-PPDL(4)-PCL(20, 50) 72.5 ± 0.8 97.6 ± 0.2 80.5 ± 1.099.0 ± 1.0 61.1 ± 0.3 85.4 ± 0.3 T-PPDL(4)-PCL(20, 40) 82.1 ± 1.6 96.3 ±0.1 85.1 ± 0.7 99.9 ± 3.2 59.2 ± 0.4 86.2 ± 0.5 T-PPDL(4)-PCL(20, 25)91.5 ± 0.1 91.4 ± 1.0 78.8 ± 0.8 98.5 ± 2.2 62.1 ± 0.7 85.8 ± 0.5T-PPDL(4)-PCL(8, 75) 17.6 ± 0.9 94.2 ± 1.4 88.0 ± 2.1 99.8 ± 0.6 39.9 ±0.7 70.5 ± 0.1 T-PPDL(4)-PCL(8, 60) 64.2 ± 2.8 96.2 ± 0.3 88.2 ± 0.9101.1 ± 1.6  48.0 ± 0.4 76.3 ± 0.4 T-PPDL(4)-PCL(8, 50) 75.2 ± 0.6 95.7± 0.3 84.1 ± 0.7 100.1 ± 0.5  55.4 ± 0.8 81.8 ± 0.3 T-PPDL(4)-PCL(8, 40)86.6 ± 0.2 91.6 ± 0.2 88.3 ± 2.1 99.1 ± 3.8 56.5 ± 0.9 83.9 ± 0.4T-PPDL(4)-PCL(8, 25) 93.8 ± 0.3 89.5 ± 0.2 80.2 ± 1.0 100.1 ± 2.6  61.1± 0.6 84.1 ± 0.4 T-PPDL(4)-PCL(4, 75)  2.0 ± 0.9 97.7 ± 0.1 76.5 ± 0.899.8 ± 0.3 36.7 ± 0.4 68.8 ± 0.3 T-PPDL(4)-PCL(4, 60) 75.5 ± 1.3 95.2 ±0.3 81.1 ± 1.5 100.5 ± 1.2  48.5 ± 0.5 82.1 ± 1.1 T-PPDL(4)-PCL(4, 50)84.9 ± 1.0 93.2 ± 3.7 68.1 ± 2.3 100.5 ± 0.8  48.0 ± 1.0 76.4 ± 1.0T-PPDL(4)-PCL(4, 40) 82.0 ± 0.8 92.0 ± 0.3 75.6 ± 4.3 99.2 ± 1.0 56.3 ±0.9 75.9 ± 0.1 T-PPDL(4)-PCL(4, 25) 93.1 ± 0.2 81.7 ± 4.1 83.8 ± 1.799.4 ± 2.4 59.5 ± 1.2 83.1 ± 0.4

Experiment C

For determining the one-step programming properties of thetriple-shape-memory networks, the sample is stretched at the temperatureT_(high) from the permanent shape C with the elongation ε_(C) into theshape ε⁰ _(A). After a waiting period of seven minutes, the sample iscooled under controlled tension with a cooling grade of 5 K·min⁻¹,whereby the sample acquires the elongation ε⁰ _(Aload). The sample isrelaxed after 10 minutes, which results in the elongation ε_(A) and theshape A, respectively. The sample is subsequently recovered, asdescribed in Bellin et al.

$\begin{matrix}{{R_{f}(N)} = \frac{{ɛ_{A}(N)} - {ɛ_{C}\left( {N - 1} \right)}}{{ɛ_{Aload}(N)} - {ɛ_{C}\left( {N - 1} \right)}}} & (1) \\{{R_{r}(N)} = \frac{{ɛ_{A}(N)} - {ɛ_{C}(N)}}{{ɛ_{A}(N)} - {ɛ_{C}\left( {N - 1} \right)}}} & (2)\end{matrix}$

TABLE 8 Shape-memory properties of the polymer networks according to thepoly-condensation method A after one-step programming. R_(f) R_(r)T_(sw1) T_(sw2) Designation [%] [%] [° C.] [° C.] T-PPDL(4)-PCL(20, 60)97.2 ± 0.4 98.8 ± 0.8 60.6 ± 0.1 80.2 ± 0.6 T-PPDL(4)-PCL(8, 60) 98.2 ±0.2 98.2 ± 0.9 49.8 ± 0.2 75.4 ± 0.4 T-PPDL(4)-PCL(4, 50) 95.8 ± 0.399.3 ± 0.2 46.5 ± 0.8 78.3 ± 0.3

Experiment D

For determining the triple-shape-memory properties with cold stretching,the sample is stretched at the temperature T_(low) from the permanentshape C with the elongation ε_(C) into the shape ε⁰ _(A), kept undertension for five minutes and then relaxed, whereby the sample acquiresthe elongation ε_(A) and the shape A, respectively. The recovery of thesample is then performed as described in Bellin et al. The cycle isrepeated four times, the stretch fixation ratio R_(f) and the stretchrecovery ratio R_(r) in the cycle N are determined in the mannerdescribed in experiment C.

TABLE 9 Shape-memory properties of the polymer networks according to thepoly-condensation method A after cold stretching. R_(f) R_(r) T_(sw1)T_(sw2) Designation [%] [%] [° C.] [° C.] T-PPDL(4)-PCL(20, 75) 78.8 ±0.2 99.8 ± 0.3 62.1 ± 0.1 83.5 ± 0.5 T-PPDL(4)-PCL(20, 50) 76.9 ± 0.399.9 ± 1.1 60.3 ± 0.3 75.8 ± 0.5 T-PPDL(4)-T-PCL(8, 50) 72.2 ± 0.3 99.7± 0.2 56.1 ± 0.6 82.6 ± 0.4 PPDL(4)-PCL(4, 50) 64.8 ± 0.3 97.7 ± 0.547.8 ± 0.6 81.5 ± 0.3

Experiment E

For determining the shape-memory properties, a fourfold cyclicthermo-mechanical experiment was created. The sample was herebystretched at T_(prog) from the permanent shape C with the elongationε_(C) into the shape ε⁰ _(A) (100% and 150%, respectively), kept undertension for five minutes and subsequently cooled under controlledtension with a cooling grade of 5 K·min⁻¹, whereby the sample attainsthe elongation ε⁰ _(Aload). After 10 minutes, the sample is relaxed,resulting in the elongation ε_(A) and the shape A, respectively.Recovery is performed by heating to T_(high)=115° C. at a heating rateof 1 K·min⁻¹. To eliminate the previous thermal history of the sample,T_(prog)=90° C. was selected in the first cycle. In the subsequent threecycles, 30, 60 and 90° C. were selected for T_(prog). The switchingtemperatures were determined in the same manner as described inexperiment B.

TABLE 10 Temperature memory properties of the polymer network accordingto the poly-condensation method A. T_(prog) = 30° C. T_(prog) = 60° C.T_(prog) = 90° C. R_(f) R_(r) T_(sw) R_(f) R_(r) T_(sw) R_(f) R_(r)T_(sw) Designation [%] [%] [° C.] [%] [%] [° C.] [%] [%] [° C.]T-PPDL(4)-PCL(8, 25) 81.9 98.1 29.2 93.4 96.9 59.0 98.6 99.6 78.4T-PPDL(4)-PCL(4, 40) 81.6 100.2 28.6 91.4 97.3 59.3 97.4 99.9 75.0T-PPDL(4)-PCL(4, 25) 81.1 97.6 29.1 92.0 101.8 59.0 98.4 101.0 81.1

Experiment F

For determining the reversible triple-shape-memory properties underconstant tension, the sample is stretched at T_(high) from the permanentshape C with the tension σ_(C) into the shape ε⁰ _(C). After waiting for10 minutes, the sample is cooled under constant tension σ_(C) to T_(low)with a cooling grade between 0.1 and 2 K/min, resulting in a two-stageelongation of the sample to the shapes B and A with the elongationsε_(B) and ε_(A). After 10 minutes at T_(low), the sample is heated toT_(high) with a heating rate of 1 K/min, whereby the shapes B and C arestepwise recovered.

TABLE 11 Reversible triple-shape-memory properties of the polymernetworks according to the poly-condensation method A under constanttension. σ_(c) T_(sw)(C→B) T_(sw)(B→A) T_(sw)(A→B) T_(sw)(B→C)Δε_(rel)(A→B) Δε_(rel)(B→C) Network-ID [MPa] [° C.] [° C.] [° C.] [° C.][%] [%] T-PPDL(4)- 0.6 69.4 37.3 45.3 78.5 9 91 PCL(8, 50) T-PPDL(3)-1.0 60.5 32.6 43.2 75.7 22 78 PCL(8, 50)Preparation of Multilayer Materials

The polymer networks prepared with the polymerization method B weresynthesized in layers having a thickness of 0.5 mm. The individualpolymer layers are programmed according to the Experiment B. The degreeof this mono-directional stretching can be selected over a wide range.In a demonstration experiment, two layers were glued together, whereinone layer was pre-stretched by 20%. However, the programming directionof the layers may also deviate from one another after gluing.Cyanacrylate chemistry was used for gluing to attain a solid andpermanent bond between the two layers.

The expected mechanical properties of the composite materials can becalculated with the help of computer modeling studies. These modelingstudies provide details for programming and stacking the layers forattaining particular shape changes of the material.

FIG. 3 shows layer systems made of triple-shape-memory polymers. FIG. 4shows individual layers with a 3-D profile, which can be programmed in aplanar structure and form a layer system in conjunction with otherplanar or planar-programmed layers. FIG. 5 shows a layer system oflayers stacked above one another on a surface X; the stacked layers arecut at arbitrary angles into layers and can then be stacked to form newlayer systems. FIG. 6 shows reversible triple-shape-memory properties ofthe network a: T-PPDL(4)-PCL(8,50) at a tension of 0.6 MPa; b:T-PPDL(3)-PCL(8,50) at a tension of 1 MPa.

We claim:
 1. A method for producing layer systems from polymershape-memory materials, comprising the steps of: a) providing at leasttwo layers of polymer shape-memory materials; and b) producing a layersystem of the at least two layers by reactive gluing, wherein the twolayers are differentiated from each other in their programming, shapeand composition.
 2. The method according to claim 1, wherein the layersare planar or are provided with a three-dimensional profile.
 3. Themethod according to claim 1, wherein the layers have a different layerthickness.
 4. The method according to claim 1, wherein the layers aremade of a polymer matrix with integrated shape-memory polymer fibers. 5.The method according to claim 1, wherein the layers have differentdegrees of programming and/or a different programming orientation. 6.The method according to claim 1, wherein the layers are programmedmono-directionally or multi-directionally.